-# cert.py
+##
+# Geniwrapper uses two crypto libraries: pyOpenSSL and M2Crypto to implement
+# the necessary crypto functionality. Ideally just one of these libraries
+# would be used, but unfortunately each of these libraries is independently
+# lacking. The pyOpenSSL library is missing many necessary functions, and
+# the M2Crypto library has crashed inside of some of the functions. The
+# design decision is to use pyOpenSSL whenever possible as it seems more
+# stable, and only use M2Crypto for those functions that are not possible
+# in pyOpenSSL.
#
-# a general purpose class for dealing with certificates
-#
-# this class serves as an interface between a lower-level X.509 certificate
-# library such as pyOpenSSL or M2Crypto. Currently both of these libraries
-# are being used due to lack of functionality in pyOpenSSL and some apparant
-# bugs in M2Crypto
+# This module exports two classes: Keypair and Certificate.
+##
+import os
+import tempfile
from OpenSSL import crypto
import M2Crypto
from M2Crypto import X509
from M2Crypto import EVP
-# Keypair
-#
-# represents a private/public key pair, or a public key
+from excep import *
+
+##
+# Public-private key pairs are implemented by the Keypair class.
+# A Keypair object may represent both a public and private key pair, or it
+# may represent only a public key (this usage is consistent with OpenSSL).
class Keypair:
key = None # public/private keypair
m2key = None # public key (m2crypto format)
+ ##
+ # Creates a Keypair object
+ # @param create If create==True, creates a new public/private key and
+ # stores it in the object
+ # @param string If string!=None, load the keypair from the string (PEM)
+ # @param filename If filename!=None, load the keypair from the file
+
def __init__(self, create=False, string=None, filename=None):
if create:
self.create()
if filename:
self.load_from_file(filename)
- def create(self):
+ ##
+ # Create a RSA public/private key pair and store it inside the keypair object
+
+ def create(self):\r
self.key = crypto.PKey()
self.key.generate_key(crypto.TYPE_RSA, 1024)
+ ##
+ # Save the private key to a file
+ # @param filename name of file to store the keypair in
+
def save_to_file(self, filename):
open(filename, 'w').write(self.as_pem())
+ ##
+ # Load the private key from a file. Implicity the private key includes the public key.
+
def load_from_file(self, filename):
buffer = open(filename, 'r').read()
self.load_from_string(buffer)
+ ##
+ # Load the private key from a string. Implicitly the private key includes the public key.
+
def load_from_string(self, string):
self.key = crypto.load_privatekey(crypto.FILETYPE_PEM, string)
self.m2key = M2Crypto.EVP.load_key_string(string)
+ ##
+ # Load the public key from a string. No private key is loaded.
+
+ def load_pubkey_from_file(self, filename):
+ # load the m2 public key
+ m2rsakey = M2Crypto.RSA.load_pub_key(filename)
+ self.m2key = M2Crypto.EVP.PKey()
+ self.m2key.assign_rsa(m2rsakey)
+
+ # create an m2 x509 cert
+ m2name = M2Crypto.X509.X509_Name()
+ m2name.add_entry_by_txt(field="CN", type=0x1001, entry="junk", len=-1, loc=-1, set=0)
+ m2x509 = M2Crypto.X509.X509()
+ m2x509.set_pubkey(self.m2key)
+ m2x509.set_serial_number(0)
+ m2x509.set_issuer_name(m2name)
+ m2x509.set_subject_name(m2name)
+ ASN1 = M2Crypto.ASN1.ASN1_UTCTIME()
+ ASN1.set_time(500)
+ m2x509.set_not_before(ASN1)
+ m2x509.set_not_after(ASN1)
+ junk_key = Keypair(create=True)
+ m2x509.sign(pkey=junk_key.get_m2_pkey(), md="sha1")
+
+ # convert the m2 x509 cert to a pyopenssl x509
+ m2pem = m2x509.as_pem()
+ pyx509 = crypto.load_certificate(crypto.FILETYPE_PEM, m2pem)
+
+ # get the pyopenssl pkey from the pyopenssl x509
+ self.key = pyx509.get_pubkey()
+
+ ##
+ # Load the public key from a string. No private key is loaded.
+
+ def load_pubkey_from_string(self, string):
+ (f, fn) = tempfile.mkstemp()
+ os.write(f, string)
+ os.close(f)
+ self.load_pubkey_from_file(fn)
+ os.remove(fn)
+
+ ##
+ # Return the private key in PEM format.
+
def as_pem(self):
return crypto.dump_privatekey(crypto.FILETYPE_PEM, self.key)
+ ##
+ # Return an OpenSSL pkey object
+
def get_m2_pkey(self):
if not self.m2key:
self.m2key = M2Crypto.EVP.load_key_string(self.as_pem())
return self.m2key
+ ##
+ # Given another Keypair object, return TRUE if the two keys are the same.
+
def get_openssl_pkey(self):
return self.key
def is_same(self, pkey):
return self.as_pem() == pkey.as_pem()
-# Certificate
-#
-# Represents an X.509 certificate. Support is included for a list of
-# certificates by use of a "parent" member. See load_from_string() and
-# save_to_string() for insight into how a recursive chain of certs is
-# serialized.
+##
+# The certificate class implements a general purpose X509 certificate, making
+# use of the appropriate pyOpenSSL or M2Crypto abstractions. It also adds
+# several addition features, such as the ability to maintain a chain of
+# parent certificates, and storage of application-specific data.
#
-# Certificates support an application-defined "data" field, which is
-# stored in the subjectAltName field of the X.509 certificate.
+# Certificates include the ability to maintain a chain of parents. Each\r
+# certificate includes a pointer to it's parent certificate. When loaded\r
+# from a file or a string, the parent chain will be automatically loaded.\r
+# When saving a certificate to a file or a string, the caller can choose\r
+# whether to save the parent certificates as well.\r
class Certificate:
digest = "md5"
issuerSubject = None
parent = None
+ ##
+ # Create a certificate object.
+ #\r
+ # @param create If create==True, then also create a blank X509 certificate.\r
+ # @param subject If subject!=None, then create a blank certificate and set\r
+ # it's subject name.\r
+ # @param string If string!=None, load the certficate from the string.\r
+ # @param filename If filename!=None, load the certficiate from the file.\r
+
def __init__(self, create=False, subject=None, string=None, filename=None):
if create or subject:
self.create()
if filename:
self.load_from_file(filename)
+ ##
+ # Create a blank X509 certificate and store it in this object.
+
def create(self):
self.cert = crypto.X509()
self.cert.set_serial_number(1)
self.cert.gmtime_adj_notBefore(0)
self.cert.gmtime_adj_notAfter(60*60*24*365*5) # five years
+ ##
+ # Given a pyOpenSSL X509 object, store that object inside of this
+ # certificate object.
+
def load_from_pyopenssl_x509(self, x509):
self.cert = x509
+ ##
+ # Load the certificate from a string
+
def load_from_string(self, string):
# if it is a chain of multiple certs, then split off the first one and
# load it
# if there are more certs, then create a parent and let the parent load
# itself from the remainder of the string
if len(parts) > 1:
- self.parent = Certificate()
+ self.parent = self.__class__()
self.parent.load_from_string(parts[1])
+ ##
+ # Load the certificate from a file
def load_from_file(self, filename):
file = open(filename)
string = file.read()
self.load_from_string(string)
+ ##
+ # Save the certificate to a string.
+ #
+ # @param save_parents If save_parents==True, then also save the parent certificates.
+
def save_to_string(self, save_parents=False):
string = crypto.dump_certificate(crypto.FILETYPE_PEM, self.cert)
if save_parents and self.parent:
string = string + "-----parent-----" + self.parent.save_to_string(save_parents)
return string
+ ##
+ # Save the certificate to a file.
+ # @param save_parents If save_parents==True, then also save the parent certificates.
+
def save_to_file(self, filename, save_parents=False):
string = self.save_to_string(save_parents=save_parents)
open(filename, 'w').write(string)
+ ##
+ # Sets the issuer private key and name
+ # @param key Keypair object containing the private key of the issuer
+ # @param subject String containing the name of the issuer
+ # @param cert (optional) Certificate object containing the name of the issuer
+
def set_issuer(self, key, subject=None, cert=None):
self.issuerKey = key
if subject:
assert(subject)
self.issuerSubject = subject
+ ##
+ # Get the issuer name
+
def get_issuer(self, which="CN"):
x = self.cert.get_issuer()
return getattr(x, which)
+ ##
+ # Set the subject name of the certificate
+
def set_subject(self, name):
req = crypto.X509Req()
subj = req.get_subject()
else:
setattr(subj, "CN", name)
self.cert.set_subject(subj)
+ ##
+ # Get the subject name of the certificate
def get_subject(self, which="CN"):
x = self.cert.get_subject()
return getattr(x, which)
+ ##
+ # Get the public key of the certificate.
+ #
+ # @param key Keypair object containing the public key
+
def set_pubkey(self, key):
assert(isinstance(key, Keypair))
self.cert.set_pubkey(key.get_openssl_pkey())
+ ##
+ # Get the public key of the certificate.
+ # It is returned in the form of a Keypair object.
+
def get_pubkey(self):
m2x509 = X509.load_cert_string(self.save_to_string())
pkey = Keypair()
pkey.m2key = m2x509.get_pubkey()
return pkey
+ ##
+ # Add an X509 extension to the certificate. Add_extension can only be called
+ # once for a particular extension name, due to limitations in the underlying
+ # library.
+ #
+ # @param name string containing name of extension
+ # @param value string containing value of the extension
+
def add_extension(self, name, critical, value):
ext = crypto.X509Extension (name, critical, value)
self.cert.add_extensions([ext])
+ ##
+ # Get an X509 extension from the certificate
+
def get_extension(self, name):
# pyOpenSSL does not have a way to get extensions
m2x509 = X509.load_cert_string(self.save_to_string())
value = m2x509.get_ext(name).get_value()
return value
+ ##
+ # Set_data is a wrapper around add_extension. It stores the parameter str in
+ # the X509 subject_alt_name extension. Set_data can only be called once, due
+ # to limitations in the underlying library.
+
def set_data(self, str):
# pyOpenSSL only allows us to add extensions, so if we try to set the
# same extension more than once, it will not work
self.data = str
self.add_extension("subjectAltName", 0, "URI:http://" + str)
+ ##
+ # Return the data string that was previously set with set_data
+
def get_data(self):
if self.data:
return self.data
self.data = uri[11:]
return self.data
+ ##
+ # Sign the certificate using the issuer private key and issuer subject previous set with set_issuer().
+
def sign(self):
assert self.cert != None
assert self.issuerSubject != None
self.cert.set_issuer(self.issuerSubject)
self.cert.sign(self.issuerKey.get_openssl_pkey(), self.digest)
+ ##
+ # Verify the authenticity of a certificate.
+ # @param pkey is a Keypair object representing a public key. If Pkey
+ # did not sign the certificate, then an exception will be thrown.
+\r
def verify(self, pkey):
# pyOpenSSL does not have a way to verify signatures
m2x509 = X509.load_cert_string(self.save_to_string())
# except:
# return 0
+ ##
+ # Return True if pkey is identical to the public key that is contained in the certificate.
+ # @param pkey Keypair object
+
def is_pubkey(self, pkey):
return self.get_pubkey().is_same(pkey)
+ ##
+ # Given a certificate cert, verify that this certificate was signed by the
+ # public key contained in cert. Throw an exception otherwise.
+ #
+ # @param cert certificate object
+
def is_signed_by_cert(self, cert):
k = cert.get_pubkey()
result = self.verify(k)
return result
+ ##
+ # Set the parent certficiate.
+ #
+ # @param p certificate object.
+
def set_parent(self, p):
self.parent = p
+ ##
+ # Return the certificate object of the parent of this certificate.
+
def get_parent(self):
return self.parent
+ ##
+ # Verification examines a chain of certificates to ensure that each parent
+ # signs the child, and that some certificate in the chain is signed by a
+ # trusted certificate.
+ #
+ # Verification is a basic recursion: <pre>
+ # if this_certificate was signed by trusted_certs:\r
+ # return\r
+ # else\r
+ # return verify_chain(parent, trusted_certs)\r
+ # </pre>\r
+ #\r
+ # At each recursion, the parent is tested to ensure that it did sign the
+ # child. If a parent did not sign a child, then an exception is thrown. If
+ # the bottom of the recursion is reached and the certificate does not match
+ # a trusted root, then an exception is thrown.
+ #
+ # @param Trusted_certs is a list of certificates that are trusted.\r
+ #
+
def verify_chain(self, trusted_certs = None):
# Verify a chain of certificates. Each certificate must be signed by
# the public key contained in it's parent. The chain is recursed
# TODO: verify expiration of trusted_cert ?
if self.is_signed_by_cert(trusted_cert):
#print self.get_subject(), "is signed by a root"
- return True
+ return
# if there is no parent, then no way to verify the chain
if not self.parent:
#print self.get_subject(), "has no parent"
- return False
+ raise CertMissingParent(self.get_subject())
# if it wasn't signed by the parent...
if not self.is_signed_by_cert(self.parent):
#print self.get_subject(), "is not signed by parent"
- return False
+ return CertNotSignedByParent(self.get_subject())
# if the parent isn't verified...
- if not self.parent.verify_chain(trusted_certs):
- #print self.get_subject(), "parent does not verify"
- return False
+ self.parent.verify_chain(trusted_certs)
- return True
+ return
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